1. Field of the Invention
The present invention relates to a glass ceramic sintered product which is best suited as an insulating substrate used in a package for accommodating semiconductor devices and in a multi-layer wiring board, and to a process for production thereof.
2. Description of the Prior Art
A rapid development in the information communications technology in recent years has required an increase in the operation speed of the semiconductor devices accompanied by an increase in the sizes thereof and, hence, by a demand for decreasing the resistance of the wiring layer in the wiring board mounting such devices in order to decrease signal transmission losses. To meet this demand, therefore, there has been proposed a wiring board using, as an insulating substrate, a glass ceramics that can be densely formed through the firing at a temperature which is not higher than 1000xc2x0 C. and can be co-fired together with a wiring layer which is chiefly composed of a low-resistance metal such as silver, copper or gold.
For example, Japanese Unexamined Patent Publication (Kokai) No. 141458/1990 discloses a glass ceramics obtained by adding an Al2O3 powder and a celsian (BaAl2Si2O8) powder to a glass powder which contains SiO2, Al2O3, CaO, MgO and B2O3, and describes that even when copper is fired at non-oxidizing atmosphere to form a wiring layer, use of the above glass ceramics as a material of the insulating substrate makes it possible to obtain a wiring board in which carbon is remaining in small amounts without impairing binder-removing property.
Further, Japanese Unexamined Patent Publication (Kokai) No. 305770/1994 discloses a glass ceramics obtained by adding an Al2O3 powder, a celsian powder and an anorthite powder to a glass powder which contains SiO2, B2O3, CaO, BaO, Al2O3, oxides of alkali metals (Li, Na, K), MgO, ZnO, TiO2, and ZrO2, and describes that the above glass ceramics can be fired even in a nonoxidizing atmosphere, and use of the above glass ceramics makes it possible to obtain an insulating substrate having a low dielectric constant and a strength of as large as 2700 kg/cm2.
However, the sintered products obtained from the above-mentioned conventional glass ceramics are not still satisfactory with respect to the mechanical strength as compared to the conventional insulating substrate materials such as aluminous sintered materials, and from which it is not possible to obtain an insulating substrate having a strength of higher than, for example, 2700 kg/cm2. They, further, have a defect of low thermal conductivity. That is, the semiconductor devices that are fabricated in large sizes and that work at high speeds are also accompanied by an increase in the amount of heat that is generated. As a result, the wiring board which uses, as an insulating substrate, a glass ceramic sintered product having a low thermal conductivity arouses such problems as an increased heat resistance and decreased mechanical reliability.
Besides, the conventional glass ceramic sintered products have low Young""s moduli. In the case of a package for holding semiconductor devices using the above sintered product as an insulating substrate, for example, the insulating substrate itself is deformed if a metal member is adhered to the surface of the insulating substrate, the metal member being a heat-radiating plate such as-metallic heat sink or heat spreader, or a sealing metal such as a lid or a seal-ring for air-tight sealing by using a closure. Also, when a sealing resin such as a potting agent or an underfilling agent is adhered to the surface of the insulating substrate, the insulating substrate is deformed itself. Therefore, a portion mounting (primarily mounting) of the semiconductor device (chip) is distorted and, in the worst case, the mounting portion is destroyed or the chip is destroyed. Further, when the wiring board having such an insulating substrate is mounted (secondary mounting) on a printed board or the like, the insulating substrate is warped to a large degree due to a difference in the thermal expansion between the insulating substrate and the printed board and, further, due to a small Young""s modulus of the insulating substrate, arousing such a problem that the terminal portions are cracked and peeled, and reliability in the electric connection decreases.
It is therefore an object of the present invention to provide a glass ceramic sintered product having a large strength and a high Young""s modulus and which can be co-fired with a low-resistance metal such as silver, copper or gold, and a method of preparing the same.
According to the present invention, there is provided a glass ceramic sintered product obtained by firing a molded article of a mixed powder of a glass powder and a ceramic powder, wherein the glass ceramic sintered product contains as crystal phases:
(i) a gahnite crystal phase;
(ii) a celsian crystal phase containing needle-like crystals having an aspect ratio of not smaller than 3; and
(iii) at least one kind of crystal phase selected from the group consisting of AlN, Si3N4, SiC, Al2O3, ZrO2, 3Al2O3.2SiO2 and Mg2SiO4;
and has an open porosity of not larger than 0.3%.
According to the present invention, there is provided a process for producing a glass ceramic sintered product, comprising the steps of:
preparing a glass powder contains;
10 to 35% by weight of SiO2,
1 to 20% by weight of Al2O3,
6 to 25% by weight of MgO and/or ZnO,
5 to 30% by weight of B2O3, and
10 to 40% by weight of BaO,
mixing the glass powder and at least one kind of ceramic powder selected from the group consisting of AlN, Si3N4, Al2O3, ZrO2, 3Al2O3.2SiO2 and Mg2SiO4 at a weight ratio of from 20:80 to 90:10;
molding the obtained mixed powder; and
firing the molded article at a temperature of not higher than 1000xc2x0 C.
According to the present invention, there is further provided a process for producing a glass ceramic sintered product, comprising the steps of:
preparing a glass powder which containing,
10 to 40% by weight of SiO2,
1 to 30% by weight of Al2O3,
6 to 25% by weight of MgO and/or ZnO,
10 to 40% by weight of BaO, and
1 to 20% by weight of Y2O3,
mixing the glass powder and an Al2O3 powder at a weight ratio of from 20:80 to 95:5;
molding the obtained mixed powder; and
firing the molded article at a temperature of not higher than 1000xc2x0 C.